Process for aromatic lactams

ABSTRACT

A process for the preparation of aromatic lactams which comprises hydrogenating an aromatic polycarboxylic acid in the presence of a Raney cobalt catalyst.

1111110 States Patent 1 1 Hollstein et al.

1 1 Mar. 27, 1973 I PROCESS FOR AROMATIC LACTAMS [75] Inventors: ElmerJ. Hollslein, Wilmington, Del; Arthur M. Brownstein, Cherry Hill, NJ.

[73] Assignee: Sun 011 Company, Philadelphia, Pa.

[22] Filed: Feb. 25, 1971 [21] Appl. N0.: 119,003

521 U.S. c1. ..260/28l, 260/501.l, 260/515 P,

260/325 51 1111. c1. .Q ..c070 39/00 58 Field of Search .260/281, 326.5PM, 325, 289 R [56] References Cited UNITED STATES PATENTS 2,079,3255/1937 Larchar.... ..260/343 2,524,392 10/1950 Leffler ..260/289R3,091,568 5/1963 Berb ..260/325 3,546,227 12/1970 Gmunder.........260/289 X 3,681,384 8/1972 Hollstein ..260/325 3,317,558 5/1967Becke et al .....260/325 3,558,647 1/1971 Sulkowski .....260/3252,351,391 6/1944 Bergstrom ..260/28l A process for the preparation ofaromatic lactams which comprises hydrogenating an aromaticpolycarboxylic acid in the presence of a Raney cobalt catalyst.

4 Claims, No Drawings PROCESS FOR AROMATIC LACIAMS This inventionrelates to an improved process for making aromatic lactams from aromaticpolycarboxylic acids. l-leretofore, complex methods or difficult toobtain intermediates were required to prepare such lactams; see, forexample, US. Pat. No. 3,317,558 (Friedrich Becke and Elly Jagla, IssuedMay 2, 1967) where o-cyanobenzyl chloride is treated with a primaryamine to obtain phthalimidine products. In contrast, the process of thisinvention permits preparation of aromatic lactams by a simple procedureinvolving hydrogenation of an aqueous solution of the diammonium salt ofan aromatic polycarboxylic acid in the presence of a Raney cobaltcatalyst. It is surprising that in the process of the inventionhydrogenation does not proceed to saturate the aromatic ring, butresults in an aromatic lactam product.

As indicated, the lactams prepared by the process of the invention arederived from aromatic polycarboxylic acids and these may becharacterized by the formula Ar(COOH),, where Ar is an aromatic nucleussuch as benzene, naphthalene, anthracene, and the like, and n is aninteger of at least 2, preferably 2 to 4. The lactam products obtainedby the process have the formula where R is an aromatic ring system suchas benzene, naphthalene, anthracene and the like and m is an integer,preferably 1 or 2.

The diammonium salt of the polycarboxylic acid is readily obtained bythe addition of 2 moles of ammonium hydroxide to 1 mole of the acid.However, in the process of the invention it is useful to employadditional ammonia in order to ensure an alkaline reaction mass. Theamount of excess ammonia is not critical, but need not exceed 20 molesper mole of acid salt.

Raney cobalt is a well-known catalytic material. As used in theprocessof this invention, the amount of the Raney cobalt is not critical, butgenerally is used in a catalytically active amount of from about 1percent to about percent by weight of the polycarboxylic acid used.

In carrying out the reaction, the diammonium salt of the acid is chargedto the reactor and aqueous ammonium hydroxide (usually about 28'percentby weight) is added and then the catalyst is added. The reactor is thenclosed and pressured with hydrogen to a pressure of about 500 to about1,000 p.s.i.g.

The reaction mass is then heated to a temperature range of from about150 to about 300C, about 250C. being preferred and hydrogen pressure isincreased to about 2,000 to 3,500 p.s.i.g. and maintained at thatpressure for the entire reaction time which normally runs from about twoto about eight, usually about four hours. The product is readilyrecovered by usual techniques (e.g., crystallization) from its aqueoussolution.

EXAMPLE 1 Into a 1 liter stainless steel rocking autoclave is charged: 1mole of the diammonium salt of phthaiic acid (previously prepared byaddition of 2 moles of ammonium hydroxide to 1 mole of phthalic acid),200 ml. of 28 percent ammonia hydroxide, and 50 gm. of freshly prepared,wet Raney cobalt. The reactor is closed and further charged withhydrogen to the pressure of 1,200 p.s.i.g. The autoclave is then heatedto 250C. and hydrogen pressure increased to 3,500 p.s.i.g. and held atthat pressure for 4 hours. From observations of pressure drop during thereaction it is indicated that about 5 moles of hydrogen were absorbed.

The reaction mass is then cooled, filtered, and the filtrate cooled topermit crystallization of the phthalimidine product. Melting point andanalysis by NMR and infrared confirm the product as phthalimidine.

EXAMPLE II Employing the essential details of Example I, except that thediammonium salt of naphthalene-2,3-dicarboxylic acid is used instead ofdiammonium phthalate, the reaction product worked up and separated isconfirmed by mass spectrographic analysis to be naphthalimidine- 2,3.

EXAMPLE III When Example I is repeated using the diammonium salt ofnaphthalene-1,8-dicarboxylic acid, the product obtained is confirmed bymass spectrographic analysis to be naphthalimidine-l ,8.

The lactam products made by the process of the invention areintermediates to substituted aromatic lactams such as the N-substitutedphthalimidines disclosed in US. Pat. No. 3,317,558 which areplasticizers and pharmaceutical intermediates. These substituted lactamsare readily made from the aromatic lactams made by the process of thisinvention by conversion of the imide group, e.g.,

where M is alkali metal and subsequent reaction with an alkyl or aralkylhalide in accordance with known procedures.

The invention claimed is:

l. The process of making aromatic lactams which consists ofhydrogenating an aqueous solution of the diammonium salt of an aromaticpolycarboxylic acid of the formula Ar(COOI-I where Ar is benzene,naphthalene or anthracene and n is an integer of 2 to 4 for a reactiontime of from about 2 to about 8 hours, at about to about 300C, at about2,000 to about 3,500 psig, and in the presence of a Raney cobaltcatalyst.

2. The process of claim 1 where the polycarboxylic acid is phthalic acidand the product is phthalimidine.

3. The process of claim 1 where the polycarboxylic acid isnaphthalene-2,3-dicarboxylic acid and the product isnaphthalimidine-2,3.

4. The process of claim 1 where the polycarboxylic acidisnaphthalene-1,8-dicarboxylic acid and the product isnaphthalimidine-1,8.

2. The process of claim 1 where the polycarboxylic acid is phthalic acidand the product is phthalimidine.
 3. The process of claim 1 where thepolycarboxylic acid is naphthalene-2,3-dicarboxylic acid and the productis naphthalimidine-2,3.
 4. The process of claim 1 where thepolycarboxylic acid is naphthalene-1,8-dicarboxylic acid and the productis naphthalimidine-1,8.